In manufacturing an electronic device, a variety of processes are performed on an object to be processed which is accommodated in a processing vessel of a processing apparatus. A cooling processing apparatus for cooling an object to be processed is used as a kind of processing apparatus. The cooling processing apparatus generally includes an electrostatic chuck, and thus the object to be processed is sucked to the electrostatic chuck by an electrostatic force.
An electrostatic chuck has a base, a first insulating layer, suction electrodes and a second insulating layer. The base is made of metal, and a flow channel through which a coolant flows is formed in the base. The first insulating layer is formed on the base. The suction electrodes are formed on the base via the first insulating layer. In addition, the second insulating layer is installed to cover the first insulating layer and the suction electrodes. If a voltage is applied to the suction electrodes of the electrostatic chuck, an electrostatic force is generated, and an object to be processed is sucked to the electrostatic chuck by the electrostatic force. As coolant flows through the flow channel, the electrostatic chuck is cooled, so that the object to be processed mounted on the electrostatic chuck is cooled.
Meanwhile, moisture inevitably exists in the processing vessel. If the moisture existing in the processing vessel is attached to the electrostatic chuck, the suction force of the electrostatic chuck may be decreased in some cases. If the moisture penetrates into the insulating layer of the electrostatic chuck, an electric discharge may be generated between the suction electrodes of the electrostatic chuck and the object to be processed or between the suction electrodes and the base. Therefore, it is required to reduce the moisture attached especially on a mounting surface of the electrostatic chuck on which the object to be processed is mounted.